1. Field of the Invention
This invention relates to hydraulic dampers for use, in one example, in suspension systems of heavy vehicles. More particularly, the invention relates to hydraulic dampers of rotary form which have the important advantages over conventional linear dampers of ruggedness and compactness.
2. Description of the Background Art
It is one problem with existing dampers that the damping characteristic varies with changes in operating conditions and in particular with changes in temperature. One object of this invention is to provide an improved hydraulic damper in which variations with temperature of the damping characteristic is much reduced.
Accordingly, the present invention consists in one aspect in a rotary hydraulic damper comprising a rotor mounted within a stator so as to define therewith at least one working chamber filled in use with hydraulic fluid; a vane for each working chamber provided on the rotor and arranged to sweep through said chamber on rotation of the rotor; and means provided in each vane to permit restricted flow of hydraulic fluid past said vane, the means comprising at least one orifice permitting turbulent flow through the vane together with valve means operating to allow increased flow when a predetermined pressure threshold is exceeded in the damper wherein each vane is provided at its radial extremity with an axially directed recess, there being located in said recess two rigid seal elements and spring means disposed between said seal elements to urge the seal elements in opposite axial directions.
The restricted flow through the orifice is capable of theoretical calculation which assists in design optimisation of the damping characteristic. Since the flow through the orifice is turbulent, it is dependent to a relatively small extent on changes in temperature so that the damping characteristic remains substantially constant over a working temperature range. The performance of the damper can therefore be close to optimum at all times.
It is generally desirable that a rotary damper should be of the smallest size consistent with the desired damping performance. This is particularly the case in the application of vehicle suspension systems where the space available on the vehicle for the damper is restricted by the design considerations of other elements of the suspension. In one particular example of a suspension system having parallel torsion bar springs extending transversely of the vehicle to support wheel arms at opposite ends, it is desirable that the radial spacing between the torsion bar springs should be minimised.